So-called low-maintenance glass (LMG) is known in the art. LMG typically includes a glass substrate supporting a plurality of thin film layers in a layer stack. A thin layer comprising titanium oxide (TiOx), usually in the anatase phase with or without some rutile presence, is provided as the outermost layer in the layer stack. The primarily anatase phase of the layer comprising TiOx allows for photocatalytic properties to be realized, which can help in providing “self-cleaning” properties advantageous for the low-maintenance glass.
To achieve the anatase phase in such coatings, it is typical to deposit titanium oxide at room temperature and then heat treat at high temperatures the coated article with the layer comprising titanium thereon. For example, heat treatment temperatures of at least 650 degrees C. are commonly used in helping to ensure that room-temperature deposited titanium oxide is converted to, or otherwise primarily is in, the anatase phase, since as-deposited layers comprising TiOx typically have an amorphous structure and do not provide much, if any, low maintenance related functionality. This sort of post-deposition activation may be accomplished by using convection or radiative sources, including flash-bulb heating, to achieve the goal of the TiOx activation. In some cases, an additional absorbing layer or an exothermic layer may be introduced to aid in converting the heat of a radiative source into activation energy. See, for example, U.S. Pat. No. 8,580,355, the entire contents of which are hereby incorporated herein by reference.
It is desirable to provide a layer comprising TiOx with low stress. This can be especially desirable in a layer stack where the layer comprising TiOx has a substantial thickness (e.g., 70 nm or greater). Unfortunately, however, layers comprising TiOx oftentimes are formed with high tensile stresses. This tendency sometimes is exaggerated in relatively thick layers comprising TiOx, especially when such layers are thermally activated. The tensile stress oftentimes results in the formation of microscopic cracks (also sometimes called “tick marks”), which can compromise the layer's integrity and lead to further damage by permitting the ingress of moisture, reactive ions, etc.
Thus, it will be appreciated that there is a need in the art for techniques for overcoming the above-described and/or other disadvantages. For example, it will be appreciated that it would be desirable to form layers comprising TiOx that lack microscopic cracks or tick marks, e.g., when provided in an anatase or primarily anatase phase.
Certain example embodiments relate to a method of making a coated article including a thin film coating supported by a substrate. An intermediate layer comprising TiOxNy, 0<y≤1, is formed, directly or indirectly, on the substrate. The as-formed intermediate layer is converted into a layer comprising or consisting essentially of TiOx by exposing the as-formed intermediate layer to a source of electromagnetic radiation, with the layer comprising or consisting essentially of TiOx being the outermost layer in the thin film coating. Electromagnetic radiation used in the converting is preferentially absorbed by the intermediate layer in an amount sufficient to heat the intermediate layer to a temperature of 500-600 degrees C. while keeping the substrate at a temperature below 500 degrees C. (more preferably below 300 degrees C.).
Certain example embodiments relate to a method of making a coated article including a thin film coating supported by a substrate. An intermediate layer comprising Ti and N is sputter-deposited, directly or indirectly, on the outermost surface the substrate. Following the sputter-deposition, the sputter-deposited intermediate layer is exposed to radiation to convert the intermediate layer into a layer comprising TiOx.
In certain example embodiments, the intermediate layer may be formed to a first thickness, and the conversion may remove nitrogen from, and introduce oxygen into, the intermediate layer, so as to cause the layer comprising or consisting essentially of TiOx to have a second thickness that is at least an 70% expansion beyond the first thickness.
The intermediate layer may be formed using room temperature or an elevated temperature of sputter deposition, in certain example embodiments.
A majority of the layer comprising or consisting essentially of TiOx may have an anatase phase, and/or the layer comprising or consisting essentially of TiOx may be photocatalytic, in certain example embodiments.
In certain example embodiments, radiation may come from a flash light operated with a series of pulses of no more than 10 ms in length.
Coated articles, insulating glass (IG) units, and/or the like, made using these methods, and products incorporating such articles, also are contemplated herein. For example, TiOx layers made using the techniques of certain example embodiments may be used in low-maintenance glass, antireflective, and/or other applications, in windows, merchandizers, and/or the like.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.